I have had several 9mm 1911s and failure to lock back is a common problem. The reason is that most makers except Colt, use the same slide stop that they use for their .45s. They will just barely catch the edge of the magazine follower and are not reliable. Get a Colt 9mm slide stop (which is considerably larger) and the slide will lock back every time. Again, DO NOT get the after market "9mm" slide stop from Ed Brown, Wilson Combat, Springfield Arms, etc. They will be the same size as the .45 slide stop. They will simply be packaged in a bag that says 9mm. Get the COLT 9mm slide stop.
Been there, done that. I know of what I speak.

marklbucla

July 28, 2008, 12:12 PM

Three of my Springfields with the Springfield stops run fine. Their recoil springs are supposedly lighter because they have heavier mainsprings.

Half my mags won't lock the slide back in my STI because of the heavier recoil spring and lighter mainspring combo.

Phil DeGraves

July 28, 2008, 01:04 PM

Does it lock back on an empty magazine when you manually cycle it? If it does, then, yes, you might have to change your recoil spring. I wouldn't think the difference to be that significant, however, unless you are not holding the gun very firmly. My girlfriend rarely gets the gun to lockback while firing, because her grip strength is limited, while it works fine when I shoot her gun.
I suppose that the heavier mainspring is just to reduce stress from the increased velocity of the slide with a lighter recoil spring. I don't know how much velocity is too much for the hammer.

farscott

July 28, 2008, 01:21 PM

In my experience, a 10-pound recoil spring is fine with the 115-grain WWB 9x19 ammo. Of course, I run a 23-pound mainspring as this gun has another barrel chambered in 9x23. I run the 10-pound spring in my hard-chromed Series '80 Colt. I know when it is time to replace the recoil spring when the empties start flying too far away or I get a failure to return to battery that can be cleared my pushing the slide closed.

As far as the slide locking open, 9x19 introduces a few variables. As has been suggested, check to see if the gun will lock back by hand. Some magazines have issues actuating the 9x19 slide stop. I have had to bend followers on Mec-Gar and Metalform magazines to get them to reliably actuate the stop. Some companies also ship .45 stops where 9x19 stops should be. My 9x19 STI Trojan 5.0 came with a stop clearly marked ".45". It also runs best with a 12-pound recoil spring. So each gun is its own puzzle. The Colt part, while expensive, is a true 9x19 part.